Shipborne mobile equipment: AIS unit requirements
Your vessel will need to have an AIS unit installed. There are two types of AIS unit available—Class A and Class B. We’ve outlined the differences below; however, we recommend talking with your marine equipment supplier about AIS features and benefits, pricing and installation.
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AIS units: shipborne mobile equipment
FAQs about AIS
AIS units: Class A
Shipborne mobile equipment intended for vessels meeting the requirements of IMO AIS carriage requirement. Class A AIS units broadcast information:
- Every 2- to 10-seconds while underway
- Every 3-minutes while at anchor
- At a power level of 12.5 watts
Class A units broadcast the following information:
- MMSI number—unique referenceable identification
- Navigation status (as defined by the COLREGS—not only are ‘at anchor’ and ‘underway using engine’ currently defined, but ‘not under command’ is also currently defined)
- Rate of turn—right or left, 0- to 720-degrees per minute (input from rate-of-turn indicator)
- Speed over ground—1/10 knot resolution from 0- to 102-knots
- Position accuracy—differential GPS or other and an indication if Receiver Autonomous Integrity Monitoring (RAIM) processing is being used
- Longitude—to 1/10000 minute; and Latitude—to 1/10000 minute
- Course over ground—relative to true north to 1/10th degree
- True Heading—0- to 359-degrees derived from gyro input
- Time stamp—the universal time to nearest second that this information was generated
In addition, Class A AIS unit broadcasts the following information every 6-minutes:
- MMSI number—same unique identification used above, links the data above to described vessel
- IMO number—unique referenceable identification (related to ship's construction)
- Radio call sign—international call sign assigned to vessel, often used on voice radio
- Name of ship—20 characters are provided
- Type of ship/cargo—there is a table of possibilities that are available
- Dimensions of ship—to nearest metre
- Location on ship where reference point for position reports is located
- Type of position fixing device—various options from differential GPS to undefined
- Draught of ship—1/10 meter to 25.5 meters (‘air-draught’ is not provided)
- Destination—20 characters are provided
- Estimated time of Arrival at destination—month, day, hour, and minute in UTC
AIS units: Class B
Shipborne mobile equipment provides facilities not necessarily in full accord with IMO AIS carriage requirements.
The Class B is nearly identical to the Class A, except the Class B:
- Has a reporting rate less than a Class A (e.g. every 30-seconds when under 14-knots, as opposed to every 10 -seconds for Class A)
- Does not transmit the vessel’s IMO number or call sign
- Does not transmit ETA or destination
- Does not transmit navigational status
- Is only required to receive, not transmit, text safety messages
- Is only required to receive, not transmit, application identifiers (binary messages)
- Does not transmit rate of turn information
- Does not transmit maximum present static draught